I believe the proper transliteration of "Thunder Bay" is サンダーベイ. Also, I think you would usually say サンダーベイに行ってきました, "I went to Thunder Bay (and came back)," rather than サンダーベイへ行ってきました "I went toward/in the direction of Thunder Bay (and came back)."

Usually "drive" is written ドライブ but that also carries the connotation of "going for a drive," i.e. driving for the pleasure of driving and/or sightseeing. In this case you could leave that off and just say ぜんぶで十八時間ぐらいかかりました.

When you're making a bifacial stone tool, you first work the material down into a rough biface, which is called a "preform" or "blank". From here, you just have to put the finishing touches on it to make it into a proper tool, although you could also just keep knocking flakes off this as a sort of bifacial core; using the flakes as flake tools.